This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Nitric Oxide (NO) is a small molecule present in the exhaled breath of humans, both adults and children. The concentration of NO in the exhaled breath increases in inflammatory disease states such as asthma, and might be useful marker of disease status. Currently, there is limited information on the mechanism which effect the amount of NO in the exhaled breath. The objective of this research plan is to collect and characterize experimental exhalation NO profiles using a fast-response NO analyzer analyzer in people who have healthy lungs or those suffering from an inflammatory lung disease. In addition, NO will from an outside source will be used to measure the rate of NO transfer across the tissue membranes in the lungs. These procedures are relatively simple and have a very low risk of adverse events in both adults and children. Interpretation of the experimental data will be facilitated through theoretical modeling of NO exchange within the airways. Successfully predicting the exhalation profile will improve our understanding of the physiology of NO exchange, its role in inflammatory lung diseases, and help in our effort to utilize this non-invasive marker as a clinical tool.